This parser supports the full W3C standard, the
complete grammar can be found under http://www.w3.org/TR/xmlschema11-2/#regexs
and extensions for all missing set operations, intersection, difference, exclusive or, interleave, complement

Documentation

The Syntax of the W3C XML Schema spec is extended by
further useful set operations, like intersection, difference, exor.
Subexpression match becomes possible with "named" pairs of parentheses.
The multi char escape sequence \a represents any Unicode char,
The multi char escape sequence \A represents any Unicode word, (\A = \a*).
All syntactically wrong inputs are mapped to the Zero expression representing the
empty set of words. Zero contains as data field a string for an error message.
So error checking after parsing becomes possible by checking against Zero (isZero predicate)